US VP urges Tehran to hold direct talks with US over nuclear program, adds Iran has the "burden of proof" over its behavior.

The window of opportunity for diplomacy over Iran’s nuclear program “will not be
opened indefinitely,” US Vice President Joe Biden warned in an interview with
the German daily Süddeutsche Zeitung on Friday.

The vice president said
the “burden of proof” on its nuclear program is on Tehran. “[Iran has] forfeited
the confidence of the international community, and they will have to continue
reckoning with crippling sanctions and increasing pressure,” Biden told the
German daily.

He urged Tehran to hold diplomatic talks and even take part
in direct negotiations with the US, saying it is the “time and place” for
successful diplomacy.

Biden told Süddeutsche Zeitung that Iran developing
a nuclear bomb is a “threat to the national security of the United States,” and
that the US “will stop Iran from getting a nuclear weapon.”

The White
House said on Thursday that Iran’s installation of advanced uranium enrichment
machines would be a “provocative step” in further violation of United Nations
resolutions against Tehran’s nuclear program.

Iran, in a letter to the
International Atomic Energy Agency, said it would introduce new centrifuges to
its main enrichment plant near the central town of Natanz, according to an IAEA
communication to member states seen by Reuters.

Such a step could enable
Iran to enrich uranium much faster than it can at the moment.

Biden set
out on a European tour during which he was to meet with Syrian opposition leader
Mouaz Alkhatib on Saturday to discuss US concerns about the Syrian conflict with
representatives from Russia and the UN.

He was scheduled to meet with
German Chancellor Angela Merkel in Berlin on Friday, French President François
Hollande on Monday, and British Prime Minister David Cameron on
Tuesday.

On Thursday, outgoing US Secretary of State Hillary Clinton
expressed concern over increasing involvement of Iran in the Syrian conflict,
including sending people and weapons to support the Assad regime.